Subject: Summary of frontier orbital enquiry

From: "Yeoh Hak Koon" <[email-masked]>
Date: Wed, 17 May 2000 11:21:22 +0800

Dear Colleagues,

A summary for whoever interested :

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My questions on Fukui's frontier orbital theory :
(a) Is his theory still valid, i.e. not overtaken by another better 
theory?
(b) What improvements had gone into the treatment of 
superdelocalizability?
(c) Has this theory been successful in more complicated molecules like 
metal complex catalysts?

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I got responses mainly on part (a), thanks to Peder Svensson, Eldbj=F8rg 
Sofie Heimstadas (& Alan Shusterman's forwarded email), Andreas Klamt
and E. Lewars. 

Answers follow (edited and abridged) :

  1.. Basic assumption for applicability : the transition state must be
reactant-like.  However, "one could of course draw conclusions from the
FOs of the product if one knows that the TS is product-like".
  2.. Superdelocalizability is available on MOPAC, and is used in QSAR,
but interpretation (+/- signs) and superiority was not certain.
  3.. Superdelocalizability must take into account the MO energies of
the interacting orbitals in the nucleophile and the electrophile to be
truthful to its original definition.
  4.. An improved concept for local frontier orbital descriptors is in
Chemosphere 1993, 26, 1273-1289
  5.. However, the frontier orbital concept was criticised on not having
a real theoretical basis.  Criticisms by M J S Dewar are in "A
Semiempirical Life", ACS, Washington DC, 1992, pp. 162-163; and
THEOCHEM, 1989, 200, 301.

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So, if you have more to add to parts (b) and (c), please!

Best regards,

H. K. Yeoh